Obstetric anal sphincter injuries (OASIS) in multiparous women with the use of epidural anaesthesia: A retrospective cohort study.

BACKGROUND: The use of epidural as a form of analgesia is increasingly common in labour, but this has shown to have been associated with increased rates of instrumental delivery, and prolonged second stage, resulting in increased rates of OASIS (Obstetric Anal Sphincter Injury).

AIMS: This study aimed to investigate the impact of epidural anaesthesia in multiparous women undergoing vaginal deliveries on OASIS and secondary maternal outcomes.

MATERIALS AND METHODS: A retrospective cohort study of multiparous women with singleton pregnancies delivering at term ≥37 weeks and the use of epidural analgesia in labour at a tertiary hospital in Melbourne, Victoria, Australia, the Royal Women's Hospital was undertaken between the period 2012-2018. Maternal outcomes were collated and dichotomised according to the presence of epidural use. Multiparous women with no prior history of a vaginal birth and non-cephalic presentation during labour were excluded.

RESULTS: There were 14 124 multiparous women who met the inclusion criteria; spontaneous labour is associated with an increased risk of OASIS at adjusted odds ratio (aOR) 1.46, P = 0.012. The overall rate of epidural use was 17%. Women with epidural use had significantly lower chances of sustaining OASIS in normal vaginal births and instrumental vaginal births. (1% vs 1.8%, aOR 0.49, P = 0.004). Epidural is associated with increased rates of prolonged second stage (8.5% vs 3.8%, P < 0.05), instrumental delivery (26.1% vs 4%, P < 0.05), and episiotomy use (23.8% vs 10.2%, P < 0.05).

CONCLUSION: The use of epidural analgesia in multiparous women is associated with a reduction in anal sphincter injuries.